Propulsion system



Feb. 2, 1960 M. PRECOUL 2,923,126

PROPULSION SYSTEM Filed Jan. 9, 1956 3 Sheets-Sheet 1 INVENTOR MICHEL PRECOUL y W1 Az/ Feb. 2, 1960 M. PRECOUL PROPULSION SYSTEM 5 Sheets-Sheet 2 Filed Jan. 9, 1956 INVENTOR MICHEL PRECOUL av WW M 3 Sheets-Sheet 3 INVENTOR MICHEL PRECOUL Feb. 2, 1960 M. PRECOUL PROPULSION SYSTEM Filed Jan. 9, 1956 BY WM,

WIIIIIIIIIIIIIIIIIIIIIIIIII United States Patent '0 PROPULSION SYSTEM Michel Precoul, Paris, France, assignor to Societe Technique de Recherches Industrielles et Mecaniques, Paris, France This invention relates to propulsion systems, and more particularly to rocket propulsion systems using the propulsive thrust of the combustion gases from a powder charge contained in the rocket. Such systems are widely used in connection with missiles both of the types wherein the energy for propelling the missile towards its target is supplied exclusively by the combustion of the charge carried by the missile, and of the type wherein the com bustion of a charge in the bore of a cannon is used-to provide a complement for the propulsive energy. In either case it is found desirable to complete the combustion process to an extremely short period of time in order to improve firing accuracy, thereby imparting very high instantaneous accelerations to the missile or rocket.

Such an increase in the acceleration force to which the rocket assembly is subjected on firing poses a serious mechanical problem in connection with the behavior of the propulsion charge itself. In view of the axially elongated shape of a rocket and of the charge contained in it, the charge on firing is subject to a high axial compression force and tends to collapse or break up. This sets up high local pressures in some points of the charge and may cause the latter to explode prematurely instead of burning smoothly as it should.

It is an object of this invention to provide an improved propulsion system design for rockets and missiles of the kind described. Another object is to provide an improved rocket or missile assembly which will withstand greater initial accelerations than was heretofore possible under comparable conditions. A further object is to improve the mechanical characteristics of the combustion charge in a rocket or missile, specifically for enabling the charge to withstand higher accelerations; it is, therefore, a broad object of the invention to improve accuracy of a rocket or missile incorporating a combustible charge. Further objects and advantages will appear as the disclosure proceeds.

Briefly the invention contemplates increasing the buckling strength of an axially elongated propulsive charge, i.e. the strength against axial compression forces, by dividing the charge along the axial direction into a plurality of self-supporting charge units, whereby the lengthto-diameter ratio for each unit is reduced and the buckling strength of the assembly correspondingly increased, while the total propulsive energy is retained substantially the same as would be obtained with a single undivided charge having a total length corresponding to the sum total of the length of the units.

Some exemplary embodiments of the invention will now be described in detail with reference to the accompanying drawings, given by way of illustration but not limitation of the scope of the invention, and wherein:

Fig. 1 is an axial cross sectional view of an assembly according to a first embodiment of the invention;

Fig. 2 is a similar view of another embodiment;

Figs. 3, 4 and 5 are sectional views respectively on the lines III-III, IVI V and V-V of Fig. 2;

Fig. 6 is an axial view of a. fourth embodiment;

Figs. 7 and 8 are sectionson lines VII-VH and VIII-VIII of Fig. 6 respectively;

Fig. 9 is an axial section of a modified assembly of the same general type as that shown in Fig. 6; and

Figs. 10 and 11 are sections on lines XX and XI-XI of Fig. 9 respectively.

Referring first to Fig. 1, a propulsive assembly for a rocket or the like comprises a tubular shell 1 having its front end sealed by a closure 2. The shell 1 contains a propulsive charge extending over the total length L therein and divided into two units, a rear unit E extending over a length L and a front unit E extending over a length L". Each charge unit consists of a plurality of coaxially disposed, annular cylindrical elements, there being three elements in each unit as shown herein, termed 4, 4' and 4 for the rear unit E and 4 4 and 4 for the front unit E. It should be understood that the total charge according to the invention may be axially divided into more than the two units shown herein. Moreover, while the two units have been shown as having equal lengths, it will be understood that the lengths thereof may be provided different if desired. The number of cylindrical elements in each unit may also be selected according to requirements and may be less or greater than three. 7 p

The rear charge unit E is supported at its rear end on a spider member 6 which may comprise a number of radial arms or flanges, upon the forward edge surfaces of which the unit E rests through interposed shockabsorber elements such as 3, 3 and 3" which may desirably be bonded to the unit E as with adhesive, and serve to distribute the compression forces and crushing strains throughout the full terminal area of the unit. The shock absorber elements may consist of discs of yielding combustible material such as cardboard or Celluloid, associated with metallic stiffener discs, e.g. made of aluminium or magnesium alloy, with flanged sides.

The shock absorber elements are arranged with their sembly, each of the charge units other than the rearmost yielding sides bonded to the powder charge E and with their stiff metallic sides abutted on the arms of the spider 6. The arrangements described enhance the operation of the system with regard to high firing accelerations while at the same time strengthening the assembly for purposes of handling and transportation.

The front charge unit E" is according to the invention supported independently of the rear unit. For this purpose there is provided a front supporting structure or cage 7 which is suitably abutted by a flange 7' thereof against a shoulder 1 of the shell. the charge unit E" is abutted against the structure 7 through shock-absorber elements similar to those described above.

The'front spider 7 has connected to it by an axially extending tie-rod 8 an intermediate spider 11. The tierod 8 has threaded ends connected with the central parts of both spiders 7 and 11 by nuts 10 and 9 respectively. Thus it will be seen that the front charge unit E11 froms a self-contained unit which is entirely supported form the shell 1 at the forward end thereof independently of the rear charge.

Shock absorber elements similar to the elements 3 described above are interposed between the rear end of front charge E" and the intermediate spider 11.

The presence of tie-rod 8 in the axial duct of the front charge does not practically interfere with the flow of gases therethrough, but on the other hand promotes their smooth flow through the front region of the assembly in which the said gases are less abundant than in the rear region.

It will be understood that in cases where more than two charge units are provided axially on the rocket as- The front end of one would according to the invention be mounted in a manner generally similar to that described in connection with the foremost charge E" above; i.e. there would be a front suspension spider atthefront of the assembly and there would be intermediate spiders: between the charge units connected therewith by tie-rods;-

In the form of embodiment illustrated in Fig 2} the front charge unit E" or eachof the frontchargemnits' in case more than one is provided, instead of being supported from the front spider by an axially located tie-rod -as in Fig. 1, is or are connected therewith by a plurality of peripherally disposed tierods 13. This arr-angement may be preferable in cases where it may be found desirable to provide a completelyclear axial ductl for the flow of gases throughout the full length. of the assembly and also. fon facilitating ignition transmission from the rear end. of the assembly to the front: end, as'fronr a detonator located centrally at the rear end of the assembly towards anignition relay in front of the. assembly.

Moreover the use of. a set of peripheral tie-rods reduces the bending stresses applied to thefront andintermediate suspension spiders of the system,v since the stresses exerted by the peripherally located tie-rods are applied at points adjacent to the supports, .so that they will. predominatingly develop shear rather than flexing strains. This will make it possible to reduce the cross sectional dimensions of the spiders and thereb'y' the over all weight of the system.

The tie-rods in this construction may; desirably be constituted as thin metallic struts, such as lengths of piano wire or spokes of the type manufactured for use in cycleor automobile wheels.

In the. particular form illustrated in Figs. 2 to 5, there are provided two combustible charge units Eand E" as in the Fig. 1 embodiment, each consisting: of fourcoaxial annular elements 4, 4', 4" and 4",ian'd 41, 4 4 and 4 respectively. The foremost unit E is supported in the shell 1 through the medium of suspension means comprising intermediate spider 11, a front cage 12, desirably made of a light alloy, and a set of threeperipherally disposed longitudinal tie-rods 13, of'the kind specified above. The intermediate spider 11 comprises six radial arms 11', and may be formed frornsix light" alloy sheet elements suitably formed and welded together. Three of the six radial arms 11' areshaped to define small; cylindrical recesses 11" through whichthe tie-rods 13 are made to extend;

The front spider 12' is formed withiithree corresponding recesses 12' for receiving and anchoring the foremostends of the rods 13 by means of nuts 13, and with a central annular opening 12" adapted to receive an ignition relay 15 therein and vented to allowfor'expansion of'the combustion gases from said relay. Each rod 13 atits rear end is formed with ahead portion 13" serving to anchor the rod in the spider 1-1.

In the form of construction illustrated in'Figs. 6 to 8, a-front combustion charge unit is supported from a front cage or spider 33 formed with a peripheral radial flange 34 seated upon the front peripheral end surface 35 of a front shell section 26. An intermediate spider 36 is clamped between the rear end of shell and the front end of'a rear shell section 25. The shell sections 25 and 26 are shown as being secured together by threaded engagement. A rear spider 37 is seated upon-the front end surface of the jet nozzle of the rocket assembly.

In.each.unit' the charge istherein shown as consisting of a'pair of coaxial annular chargeelements'designated 38' and'39 for the rear charge unit and 40 and 41 for the fr'ont'charge unit.

Thefront cage or spider 33 is show'niin Fig; 8' as'comprising three arcuate outer strips"42' andthree'arcuate' inner strips 43 radially aligned with the respective'outer strips. All the strips are cambered substantially concentrically with the shell outline. The'stripsare' fully secured through any appropriatemeans, as by'weldir'rg;

solder, brazing, pins or otherwise, to the body of the front cage. The intermediate spider 36 has a similar construction as will be apparent from Fig. 7, and comprises the three outer arcuate strips 44 and the three inner arcuate strips 45. The above described strips project longitudinally in a rearwarddirect'ion from the body of the associated spider. The strips of the outer set such as 42 and 44 are arranged closely to surround the outermost one of the two annular charge elements 38 and 40, and similarly the" strips of the inner or intermediate set such as 43 and 45 closely surround the innermost annular charge elements 39 and 41'. The strips are pinned to the charge elements by means of pins such as 46.

As-showri' herein, each pin 46 has a head 47 at its outer end resting. against an outermost strip 42 or 44 and extends through aligned apertures such as 48 formed in both adjacent coaxial charges and strips to maintain the assembly. The head- 47- of each pin is suitably profiled to oppose minimumresistance to gas flow, and it will be seen that-all the-heads: 47 are-located in the finished assembly in close proximity to the internal cylinder surfaces 25' and 26' of the shell sections 25 and 26, so that once the charge assemblies have been inserted into the shell the pins are prevented from escaping radially outwards and the structure is thus retained in assembled relationship. The pins 26 provide a simple and efiicient means of supporting the combustion charge elements in each unit and maintaining them against damage and premature collapse or explosion during storage, transportation and firing. Each charge unit is separately suspended from a related front spider orcage and is seated against a related rear spider, preferably through shock absorbing elements similar to those'describ'ed with reference to the first embodiment,-so that the axialacceleration. force developed during the firing period is individually taken up for each charge unit of moderate length-to-diameter ratio as previously explained.

It willbe understood that the number and arrangement of the coaxial change elements, as well as the number and arrangement of the supporting strips and the'number and arrangement of the pins such as 46, may be varied according to particular requirements while retaining the general teachings'set forth in connection with'the form of embodiment described with reference to Figs. 6 to 8.

The modification illustrated in Figs. 9 to IL is generally similar to the one just described, exceptfor the shape of the charge units used. Herein, each charge unit instead of consisting. of a plurality of coaxial annular elements as in the forms-so far described, consists of asingle perforate: block. Thus, the rear charge unit is formed asa perforate unit 49 generally comprising a pair of coaxial annular'cylinders 49' and 49" interconnected by radial arms 50, and the front unit 51 is similarly built. The means for supporting the front unit 51 are substantially the same as described with reference to Figs. 6-8, including the three radiallyspaced outer arcuate strips and three inner arcuate strips. The outer arcuate strips are arranged in peripheral engagement with the outer cylindrical contour of the charge, and the inner with that of the inner contour of the charge, the strips and charge portions being pinned together by means of pins'56.

As regards the rear unit 49 however, the supporting means are somewhat difierent. In this case the radially inner arcuate strips" are replaced by a complete tubular element 54 having perforate side walls and having its front end soldered or brazed to the inte'rmediate'spider 52; The pins 55' extendinto holes in the'walls' of the tubular element. It will be noted from Figs. 10 and 11 that the pins 55 in the'front unit'extend through the front' charge unit 51 along'lines' bisect'ing the radial arms 51" connecting -the inner with the outer section of the charge. This arrahgement'will not substantially interfere withithe' proper flow of'gases through the longi tudinal apertures in"th'e"front ch'arge unit, sinc'e th'e'volume of such gases is relatively small. In the rear charge unit however (Fig. where the flow of gases is greater, it will be noted that the pins 55 extend through the radial interconnecting arms so that they will not interpose obstacles in the gas flow.

What I claim is:

l. A powder propulsion. rocket comprising a body, a front cage and a rear cage in said body, a plurality of cylindrical tubular powder blocks forming a propulsive charge located concentrically to one another at the interior of said body and spaced therefrom between said front cage and said rear cage, means for suspending said blocks from said front cage comprising a plurality of strips fixed to said front cage and to said blocks, and said strips extending longitudinally upon a portion of the periphery of said tubular blocks.

2. In a rocket as set forth in claim 1 wherein said strips for suspending said blocks to said front cage are cambered so as to correspond in shape with said blocks.

3. A powder propulsion rocket comprising a body, a front cage and a rear cage in said body, a plurality of cylindrical tubular powder blocks forming a propulsive charge located concentrically to one another at the interior of said body and spaced therefrom between said front cage and said rear cage, a plurality of strips secured to said front cage, said blocks and strips being provided with radial holes, means for connecting said strips to said blocks comprising radial pins which traverse said radial holes in said blocks and strips.

4. In a rocket as set forth in claim 3 in which said strips for the suspension of said powder blocks to said front cage extend coaxially with said blocks and are also disposed in the same radial plane so that said radial pins may traverse a plurality of powder blocks and strips.

5. In a rocket as set forth in claim 2 wherein pins are provided connecting said strips and said concentrical powder blocks, the ends of said pins being directed towards the external surface of the strip and is enclosed between said external surface of said strip and the internal surface of said body.

6. In a rocket as set forth in claim 1 wherein said concentric blocks are fixed to said suspension strips at two points in each block by means of radial pins.

7. A powder propulsion rocket comprising a body, a front cage and a rear cage in said body, a plurality of cylindrical tubular powder blocks forming a propulsive charge located concentrically to one another at the interior of said body and spaced therefrom between said front cage and said rear cage pierced with radial holes, means for suspending said powder blocks from said front cage comprising a longitudinal tube fixed to said front cage centrally of said body provided with holes and a plurality of strips having holes therein also fixed to said front cage extending longitudinally upon a portion of the periphery of said blocks and radial pins passing through said holes in said powder blocks, strips and said central tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,404,190 Pope July 16, 1946 2,519,878 Bjork Aug. 22, 1950 2,548,972 Grisamore Apr. 17, 1951 2,623,465 Jasse Dec. 30, 1952 2,724,237 Hickman Nov. 22, 1955 2,728,295 Rubin Dec. 27, 1955 FOREIGN PATENTS 543,739 Great Britain Mar. 11, 1942 

